Variable transmittance optical filters are devices that can be used to selectively filter electromagnetic radiation. Given this ability these filters can be incorporated into a room's windows to control one or both of the intensity and frequency of the electromagnetic radiation that enters and escapes the room. The comfort of people in the room and the energy efficiency of the room can depend on how much and what kind of electromagnetic radiation the windows allow into and out of the room. Accordingly, research and development continue into methods and systems that can be used to control variable transmittance optical filters.